1. Field of the Invention
The present invention relates to a data setting method in a bonding apparatus and more particularly to a method for setting data which is used to operate a frame feeder for conveying lead frames supplied from a loader side magazine to a bonding position on the bonding stage and then further to an unloader side magazine after the completion of bonding on the lead frames.
2. Prior Art
Examples of conventional methods for conveying lead frames in a bonding apparatus such as a wire bonding apparatus, die bonding apparatus, etc. include the methods described in Japanese Patent Application Publication (Kokoku) No. S63-56122 and Japanese Patent Application Laid-Open (Kokai) No. H4-346446. In such methods, lead frames accommodated inside a loader side magazine are fed out onto the conveying path of a frame feeder by a frame pusher, and a leading end alignment (for aligning a leading end of each lead frame) of the lead frames is performed by a pair of loader side feeding claws, that comprise upper and lower claws, or by positioning pins installed on the claw holder which holds the feeding claws.
Next, each lead frame is intermittently fed by a distance that is equal to a distance between two devices (islands) provided on the lead frame. In other words, the lead frame is intermittently fed by a combination of the opening and closing action and reciprocating motion of the feeding claws so that each one of the devices (or islands) is positioned beneath a television camera installed above the bonding position. Then, the bonding pattern of the lead frame is detected by the television camera; and after a correction of any positional deviation, bonding is performed by the bonding apparatus.
When bonding is completed, the lead frame is moved one pitch by the feeding claws, so that the next device (island) is fed to a point beneath the camera; and after the operation described above, bonding is performed to the device.
When bonding is thus successively performed and completed, the lead frame is fed to the unloader side by the unloader side feeding claws that perform an action similar to that of the loader side feeding claws, so that the lead frame on which bonding has been completed is accommodated in the unloader side magazine.
Thus, in order to feed the device on the lead frame to the bonding position of the bonding stage (i. e., to a position beneath the camera), it is necessary to input lead frame conveying data into a control device beforehand. More specifically, whenever the type of lead frame to be handled changes, conveying data that meets such a lead frame needs to be inputted in the control devices.
The above-identified Japanese Patent Application Publication No. 63-56122 and Japanese Patent Application Laid-Open No. 4-346446 are silent about the method for setting the lead frame conveying data; however, such data is customarily set by the method described below. Though there are various types of lead frames to be handled, the following description will be made in regards to the lead frames 1A and 1B shown in FIGS. 8 and 9.
FIG. 8 shows a lead frame 1A having islands with a constant pitch in between, that is, the islands 2A, 2B . . . 2F have a constant pitch distance d. FIG. 9 shows a lead frame 1B having islands with an irregular pitch in between, that is, the islands 2A, 2B . . . 2F have irregular pitch d1, d2 . . . d5 instead of a constant pitch distance d as in the lead frame of FIG. 8.
In FIGS. 8 and 9, a indicates the frame length, b indicates the distance from the center of the first island 2A to the center of the last island 2F, and c indicates the distance from the leading end of the lead frame 1A or 1B to the center of the first island 2A (such distance being hereafter referred to as the "first pitch").
If the number of the islands 2A, 2B . . . 2F, indicated by n, and the distance b are set, then the constant pitch distance d can be calculated using Equation 1: EQU d=b/(n-1) Equation 1
The lead frames 1A and 1B are obtained by cutting a hoop material (continuous band-form material) into card shapes. Accordingly, in cases where there is no variation in the cutting positions of the hoop material, the first pitch c is roughly 1/2 of the constant pitch distance d though it is actually smaller than the constant pitch distance d by an amount equal to the cutting waste. Thus, for lead frames having the first pitch c roughly 1/2 of the constant pitch distance d, it is possible to feed them without colliding with each other during continuous conveyance thereof by calculating the frame length a by an equation of a=b+d. More specifically, in the case of the lead frame 1A shown in FIG. 8, it is only necessary to set the data n and b; and in the case of the lead frame 1B, it is only necessary to set the data n, b, d1, d2 . . . d5. However, there may be lead frame lots in which the lead frames 1A or 1B show a large variation in the cutting position, or cases in which the first pitch c is not roughly equal to (1/2).multidot.d in the lead frames 1B that has an irregular pitch. In the case of such lead frames 1A or 1B, it is necessary to set the frame length a and the first pitch c in addition to the data n and b or n, b, d1, d2 . . . d5 in order to prevent the lead frames from colliding with each other when the lead frames are continuously conveyed.
Accordingly, when lead frames 1A or 1B having the first pitch c roughly 1/2 of the constant pitch distance d are to be conveyed, the data n and b or n, b, d1, d2 . . . d5 are investigated by reference plotted relationships or by actual measurement, and then the numerical values of these elements are inputted into the data memory of the control device by selecting the set-mode of the apparatus. On the other hand, when lead frames 1A or 1B having the first pitch c not roughly 1/2 of the constant pitch distance d are to be conveyed, the frame length a and first pitch c are investigated in addition to the data n and b or n, b, d1, d2 . . . d5 by reference to plotted relationships or by actual measurement, and then the numerical values of these elements are inputted into the data memory of the control device by selecting the set-mode of the apparatus.
By way of these numerical value inputs, the calculation processing section of the control device calculates the constant pitch distance d for each lead frame 1A using Equation 1 described above, and the main control section of the control device outputs control signals so that portions of the lead frame 1A corresponding to the islands 2A, 2B . . . 2F are successively fed to the bonding position on the bonding stage. On the other hand, in the case of lead frames 1B, the main control section outputs control signals in accordance with the set pitches d1, d2 . . . d5 so that the portions of each lead frame 1B corresponding to the islands 2A, 2B . . . 2F are successively fed to the bonding position on the bonding stage.
Thus, theoretically, the portions of each lead frame 1A or 1B corresponding to the islands 2A, 2B . . . 2F can be successively fed to the bonding position on the bonding stage by inputting the numerical value data as seen above. However, the respective constituent elements of individual frame feeders involve certain amounts of mechanical working error and assembly error. Accordingly, the lead frames 1A or 1B are not accurately fed to the bonding position on the bonding stage merely by setting data according to plotted relationships or actual measurements.
Accordingly, after the data have been set, a check is practically made in order to ascertain whether the lead frame 1A or 1B has actually been accurately conveyed to the bonding position on the bonding stage; and this checking is accomplished by imaging the lead frame with a television camera, viewing the resulting image on a monitor screen, visually checking for any deviation in the feeding pitch, inputting any such deviation as a numerical value, and performing a fine adjustment. In other words, correction values for the deviation in the feeding pitch (feeding pitch correction values) are set when the lead frame 1A or 1B which has been fed to the bonding position on the bonding stage is fed from the first island 2A to the second island 2B, and then to the third island 2C, and so on. This correction of the deviation is repeated until the lead frame 1A or 1B is actually conveyed in an accurate manner.
In the prior art described above, whenever the type of lead frame to be handled is changed to lead frame 1A, it is necessary to set the data n, a, b and c with reference to plotted relationships or by actual measurement, and then to actually feed the lead frame 1A and correct for any deviation; similarly, whenever the type of lead frame to be handled is changed to lead frame 1B, it is necessary to set the data n, a, b, c, d1, d2 . . . d5 in the same manner as in the case of lead frame 1A, and then to actually feed the lead frame 1B and correct for any deviation. As a result, the setting of data requires a considerable amount of time. Furthermore, since the amount of deviation is determined by visual inspection using a monitor screen when fine adjustments are made for the amount of deviation, the amount of deviation cannot be accurately determined, and such fine adjustments must therefore be performed a number of times.